The present invention relates generally to improvements in a power source switch in an automatic exposure camera, and it relates more particularly to an improved power source switch in an automatic exposure camera provided with an exposure information indicating circuit.
In the automatic exposure camera, generally, electric power consumption by the light measuring circuit and the exposure time is appreciable and cannot be neglected. As a result, in an attempt to economize on electric power consumption, there is provided a normally-opened switch between the electric power source, and the light measuring circuit as well as the exposure-time control circuit, so that the switch may be brought to its closed position in association with the operation of a camera by the photographer so that current may be supplied to both the light measuring circuit and the exposure-time control circuit, only when such current is required. A conventional construction for facilitating the closing of a switch of this type is to arrange the switch as to cooperate with a release button so as to be closed when the release button is depressed. This arrangement permits the closing of the switch, immediately before the picture-taking operation, so that a reduction in the use of electric power may be most effectively achieved, and there is no possibility of the switch failing to be thrown, before the photographing sequence.
However, in the case of the prior art camera provided with an exposure information indicating circuit for indicating exposure information, based on the measurement derived from the light measuring circuit, the release button should be maintained in a half-way or semi-depressed condition so as to operate only the light measuring circuit and exposure information indicating circuit while preventing the shutter releasing operation for the purpose of confirming the exposure conditions or information. However, this procedure possesses the shortcoming in that, since the extent of the release button is initially depressed is determined by the photographer, there is a great risk of the release button being unintentionally depressed below that required for electrically energizing the respective light measuring and indicating circuits to a position initiating the photographing sequence so that an unwanted picture is taken.
In addition, with the prior art camera provided with the switch of the type above described, the stroke of the release button should be increased for actuating the switch in the course of depressing the release button. To this end, at least one of the members constituting the switch should be provided in the form of a movable contact. Accordingly, defective operation or malfunctioning will occur in the switch due to the excessive wear or damage of the contacting portions of the both contact members of the switch during their long service lives.
Furthermore, where a camera is provided with a light measurement storage circuit, that is, in the case of a TTL automatic exposure camera, object light which traverses the objective lens is first measured by the light measuring circuit, and then a movable reflecting mirror is swung out of the objective lens optical path whereupon the storage circuit is operated to electrically store the measurement derived from the light measuring circuit, before the measured object light is interrupted by the movable mirror thus swung, so that the exposure amount or time may be automatically controlled according to the measurement thus memorized or stored. In this case, during the period from the time when the light measuring circuit is activated until the shutter is released, the light measuring circuit should complete measuring the light, and the storage circuit should store the light measurement. However, the camera provided with the conventional or prior art switch fails to provide a sufficient time interval from the time the circuit energizing current is initiated to be fed in the course of depressing a release button until the shutter is released, so that if the release button is depressed too rapidly, then sufficient time may not be provided for the light measurement and storage thereof, thus leading to the failure to accurately store the measurement of the light.